In order to improve physical properties such as flex-fatigue and heat aged stock properties, it is known to employ chlorinated polymers in a rubber composition. One early patent embodying the former technique is U.S. Pat. No. 2,482,600 which discloses a rubbery composition resistant to heat deterioration for vulcanized tires, conveyor belts and the like. The composition therein described comprised from about 50-90 percent by weight of natural rubber, and 10-50 percent by weight of a mixture of polychloroprene and butadiene-acrylonitrile copolymer. While the rubber articles made with this composition would have been reinforced in a manner known at that time, such as with natural or synthetic fibers, there is no suggestion that improved adhesion between the disclosed composition and wire reinforcement or metal in general would be obtained.
U.S. Pat. No. 3,639,308 disclosed inner liner compositions which could be bonded to the inner wall surface of the carcass of a tubeless rubber tire. The compositions comprised butyl rubber or chlorinated butyl with natural rubber to provide inner liner compositions having improved resistance to air permeability and heat aging. Adhesion tests were conducted with the inner liner composition sandwiched between a ply of carcass stock and outer plies of rubberized tire cord, however, there was no suggestion that improved adhesion between this composition and metal would be obtained. U.S. Pat. No. 3,596,753 to Knapp disclosed an elastomer consisting of a mixture of a nitrile rubber and a polychloroprene to produce a heat-resistant conveyor belt having steel wire supporting inserts. Although the disclosure stated that adhesion to zinc-coated steel wires must be provided, there was no claim that the nitrile rubber-polychloroprene mixture exhibited satisfactory adhesion with the wire. In fact, for improved adhesion, the steel wire was to be coated with an agent such as a cobalt salt soluble in the elastomer.
While others have broadly disclosed natural rubber blends containing polychloroprene or chlorobutyl rubber, the presence of certain chlorinated polymers with natural rubber to improve aged adhesion between rubber skim stocks and metal reinforcement has not been described in any patents or publications of which we are aware.